Search

The Square Kilometre Array (SKA) organisation is building a low frequency (50-350 MHz) aperture array to be located in remote Western Australia. The array consists of 512-stations, each consisting of 256-dual polarisation log-periodic antennas. The stations are distributed over a distance of 80km, with the greatest density of stations located in the central core. The input bandwidth is processed in a two stage polyphase filterbank, with the first stage channeliser producing 384 x 781 kHz narrow-band channels. Each station beamforms the antennas together to form a single dual polarisation beam with a bandwidth of 300 MHz (additional beams can also be traded for bandwidth). The second stage polyphase filterbank is located in a system called the Correlator and BeamFormer (CBF) which is the topic of this paper. In the CBF the station signals are first aligned in time. Thereafter the signals are simultaneously correlated and beamformed.

In the far-infrared (FIR) / THz regime the angular (and often spectral) resolution of observing facilities is still very restricted despite the fact that this frequency range has become of prime importance for modern astrophysics. ALMA (Atacama Large Millimeter Array) with its superb sensitivity and angular resolution will only cover frequencies up to about 1 THz, while the HIFI instrument for ESA'a Herschel Space Observatory will provide limited angular resolution (10 to 30 arcsec) up to 2 THz. Observations of regions with star and planet formation require extremely high angular resolution as well as frequency resolution in the full THz regime. In order to open these regions for high-resolution astrophysics we present a study concept for a heterodyne space interferometer, ESPRIT (Exploratory Submm Space Radio-Interferometric Telescope). This mission will cover the Terahertz regime inaccessible from the ground and outside the operating range of the James Webb Space Telescope (JWST).

The far-infrared (FIR) wavelength regime has become of prime importance for astrophysics. Observations of ionic, atomic and molecular lines, many of them present in the FIR, provide important and unique information on the star and planet formation process occurring in interstellar clouds, and on the lifecycle of gas and dust in general. As these regions are heavily obscured by dust, FIR observations are the only means of getting insight in the physical and chemical conditions and their evolution. These investigations require, besides high spectral, also high angular resolution in order to match the small angular sizes of star forming cores and circum-stellar disks. We present here a mission concept, ESPRIT, which will provide both, in a wavelength regime not accessible from ground by ALMA (Atacama Large Millimeter Array), nor with JWST (James Webb Space Telescope).